1. Field of the Invention
The present invention relates to a field coil assembly of an electromagnetic clutch, and more particularly, to a field coil assembly of an electromagnetic clutch in which a grounding structure and an interconnection structure between a terminal of a power supply connector and a field coil are improved.
2. Description of the Related Art
A compressor of a refrigerant system for a vehicle operates and stops under the control of an electromagnetic clutch that regulates rotating power transferred from a vehicle engine to a rotating shaft of the compressor.
As shown in FIG. 1, a general electromagnetic clutch 101 includes a pulley 103 rotating with power received from a vehicle engine, a disc and hub assembly 105 coupled to a rotating shaft 109 of a compressor 107 so as to be attached to or detached from the pulley 103, and a field coil assembly 110 for attaching or detaching the disc and hub assembly 105 to or from the pulley 103 according to supply or interruption of power.
If power is supplied to the field coil assembly 110, the electromagnetic clutch 101 forms a magnetic field by electromagnetic force so that the disc and hub assembly 105 is attracted attached to a frictional surface of the pulley 103, thereby operating the compressor 107. Then, if the supply of power to the field coil assembly 110 is interrupted, the disc and hub assembly 105 is separated from the frictional surface of the pulley 103 due to the released electromagnetic force and elastically repulsive force of the disc and hub assembly 105, whereby the compressor 107 stops operating.
In other words, the compressor 107 operates or stops under the control of the electromagnetic clutch 101 according to whether or not to supply power to the field coil assembly 110.
The field coil assembly 110 employed in the conventional electromagnetic clutch 101 includes a field coil member 120 for generating electromagnetic force, a power connecting member 130 for connecting an external power source to the field coil member 120, and a ground terminal 150 for the field coil member 120, as shown in FIGS. 2 and 3.
Now, the field coil member 120, the power connecting member 130 and the ground terminal 150 will be described in detail.
First, the field coil member 120 includes a coil body 121 having a coil wire 122 wound in a ring shape, and a bobbin 123 receiving the coil body 121 and having a coil drawn-out portion 124 formed in a region thereof to expose both ends of the coil wire 122 that extends outward from the coil body 121.
In addition, the field coil member 120 is provided with a core ring 125 that receives the bobbin 123 having the coil body 121 received therein and is inserted into a coil receiving space of the pulley 103.
The field coil member 120 is provided with a core ring cover 127. The core ring cover 127 serves to seal an open side of the core ring 125, which receives the coil body 121 and the bobbin 123.
The field coil member 120 is provided with a flange 128. The flange 128 is coupled to one side of the core ring 125, and the flange 128 has catching portions 129 formed in a region corresponding to the coil drawn-out portion 124 of the bobbin 123, wherein the catching portions 129 are caught to or released from a sleeve 135 of the power connecting member 130, which will be described later.
In addition, the power connecting member 130 includes a connector 131 connected to an external power source, and the sleeve 135 electrically connected to the connector 131 and having terminals 140 connected to the exposed ends of the coil wire 122 of the field coil member 120.
Here, as shown in FIGS. 3a and 3b, the power connecting member 130 is configured such that the connector 131 connected to an external power source A (see FIG. 1) is formed integrally with the sleeve 135, and the terminals 140 is provided within the sleeve 135 by an insert injection molding process.
Alternatively, as shown in FIGS. 4a and 4b, upper and lower sleeves 135a and 135b may be coupled with each other to form a sleeve 135, and terminals 140 interposed between the upper and lower sleeves 135a and 135b may be electrically connected to a power supply line 133 of the connector 131.
The sleeve 135 of the power connecting member 130 has hooks 137 formed at both sides thereof in a width direction, wherein the hooks 137 are caught and engaged to the catching portions 129 formed on the flange 128 of the field coil member 120.
In addition, the terminals 140 for electrically connecting the coil body 121 of the field coil to the external power source protrude between the pair of hooks 137. Here, a connection end of the terminal 140 is open at one side thereof to have a ‘⊂’ shape such that both the ends of the coil wire 122 of the field coil member 120 may be inserted therein.
Meanwhile, the ground terminal 150 is provided at one end of a ground lead wire 151 extending from the coil body 121 of the field coil member 120 to the outside through the bobbin 123 and the core ring 125. At this time, a bushing 153 having an airtight property is coupled to the portions of the bobbin 123 and the core ring 125 through which the ground lead wire 151 passes, thereby allowing the ground lead wire 151 to be drawn out with airtight.
An assembling process of the field coil assembly 110 of the conventional electromagnetic clutch 101 so configured will be described. When the sleeve 135 of the power connecting member 130 is inserted between the catching portions 129 formed on the flange 128, the hooks 137 at both the sides of the sleeve 135 are caught to the catching portions 129, and both the ends of the coil wire 122 of the field coil member 120 are inserted into the ‘⊂’ shaped connection ends of the terminals 140.
In this state, the ‘⊂’ shaped connection ends of the terminals 140 are compressed by means of a press tool (not shown), and the compressed portions are treated through a high frequency fusing process. Then, the electrically coupling state of the end of the coil wire 122 and the connection end of the terminal 140 is maintained.
Then, the electrically connected portions between the coil wire 122 and the terminals 140 of the sleeve 135 and their surroundings are molded by an insert injection molding process, thereby preventing the electric connection portions from being exposed to the outside and penetrated by moisture. Thus, the field coil assembly 110 is completely assembled.
In addition, the ground terminal 150 is grounded to one side of a vehicle body using a coupling part (not shown), such as a screw or rivet.
However, in the field coil assembly 110 of such a conventional electromagnetic clutch 101, the ‘⊂’ shaped connection end of the terminal 140 of the sleeve 135 has a certain height and surround a vertical range of the end of the coil wire 122, so that the molded portion M formed on the electric connection portions of the coil wire 122 and the terminal 140 of the sleeve 135 and their surroundings has a great height h.
More specifically, the height h of the molded portion M is at least a sum of the height of the ‘⊂’ shaped connection end of the terminal 140 and a length of the coil wire 122 drawing upward from the ‘⊂’ shaped connection end.
Due to the height of the molded portion M, the overall appearance of the field coil assembly 110 is deteriorated.
Also, in a process of mounting the field coil assembly 110 to the coil receiving space of the pulley 103, the molded portion M of the sleeve 135 may easily interfere with surroundings due to its height h, thereby deteriorating the mountablity of the field coil assembly 10. Also, the volume occupied by the field coil assembly 110 in a vehicle is increased, thereby deteriorating a space utilization of a vehicle.
In addition, the field coil assembly 110 of such a conventional electromagnetic clutch 101 is provided with the additional ground terminal 150, which needs additional parts such as the ground lead wire 151 and the bushing 153 in addition to the ground terminal 150, thereby increasing the number of parts and assembling processes.
Also, since the ground terminal 150 grounded to the vehicle body is exposed to the outside, the exposed portion easily corrodes, thereby deteriorating the durability of the field coil assembly 110.